In the field of agricultural and light commercial dryers there are several established methods for drying solutions, slurries and particulate materials. Despite their outward differences, the established methods share common operating features. In the majority of the methods, the material to be dried is heated to a degree necessary for the liquid contained in the material to evaporate. The resulting vapor is then removed or allowed to escape from the dryer, thus yielding a drier material. However, the drying rate of such methods is limited by the particular substrate's capacity to transfer heat energy from the heat source, such as steam pipes. In most methods, the poor transfer of heat energy creates further problems of local overheating of portions of the material and uneven drying of the entire sample. Product quality lessens and fire hazards increase. Extensive agitation or tumbling of the material is often introduced in an effort to lessen the damaging effects of the overheating and uneven drying.
The energy demand of conventional methods is quite high, because the whole sample of material must be heated to the evaporation temperature to ensure adequate heat flow. Powerful electric fans are often required to blow hot air through the sample, air which is heated by using costly fuels such as propane. In the prior art systems the heated air and vaporized liquid are vented to the atmosphere. Despite the expensive high energy demand of such drying systems, little effort has been made to recapture and recycle the substantial losses of heat energy in the escaping vapor and heated air or to utilize heat generated by the dryer's equipment in the drying process itself.
In view of the increasing scarcity and cost of energy supplies, the inefficiencies and heat wastes of prior art drying techniques represent an increasingly serious problem for our society. This is particularly true in the field of agriculture, where the high energy consumption of present grain drying methods has serious economic implications both to food producers and consumers.
The present invention reduces considerably the energy demand for the drying process, and it also provides superior drying rates for solutions, slurries and solids unknown in the prior art. The present invention achieves consistent rates of evaporation and vapor removal, thereby eliminating local overheating and risk of fires, and thereby maintaining the valuable, original quality of the product. By reclaiming and recycling the energy supplies spent in the drying process, the energy demanded for the drying process is drastically reduced as compared to prior art methods.
As will be explained in detail in the specification, the present invention is not a variation of the inefficient methods known in the art, but is a revolutionary concept having broad application into wide areas of material drying, including drying sludge, concentrating fermentation liquors, dehydrating wastes, evaporating organic liquids, and numerous other applications involving drying procedures.